trigger Atask_af_up on A_Task__c (after update) {
//When change Status then update Announcement if apply
  if(trigger.isUpdate){
    A_task__c p= trigger.new[0];
    if (p.Status__c!='Not Started') {
        Announcement_Update_Status.Update_Status(p.Announcement__c);    
        }     
    }
}